Structural Study of Chemical-Vapor-Deposited Diamond Surface by High-Resolution Electron Microscopy

A structural study of the chemical-vapor-deposited (CVD) diamond surface using high-resolution electron microscopy (HREM) is presented. The CVD diamond used for HREM study was directly deposited onto molybdenum grids by a microwave plasma-assisted chemical vapor deposition method. The HREM images reveal a thin amorphous layer of which average thickness is about 0.8–1.2 nm on the as-grown diamond surface, whereas the average thickness of the surface amorphous layer is decreased to less than 0.4–0.5 nm for the samples annealed in air following deposition. When the samples annealed in air were exposed to hydrogen plasma for 10 min, a distinct damaged layer on the diamond surface was observed. HREM study demonstrates that such a damaged layer consists of amorphous solid and small diamond bumps, and its thickness is about 1.5–2 nm. It is also found that hydrogen plasma has a much higher etching speed in the rough regions, edges and protuberances than that in the smooth regions on the diamond surface.